Typically, an ink supply station is responsible for delivering ink through an ink tube to a print head in an inkjet printing device. The ink supply station includes an ink supply which contains the ink. Further, the ink tube is connected to the print head via a septum. Typically, the ink supply station is mounted at a positive Z elevation above the print head, a negative Z elevation below the print head or the same elevation as the print head. Generally, in a pressurization sequence, an air solenoid valve is opened and the ink supply is pressurized to approximately about 6 pound-force per square inch (PSI) using an air pump. Upon the pressure on the ink supply reaching to approximately about 6 PSI, an ink solenoid valve is opened to push the ink out of the ink tube. In the pressurized state, the ink supply is locked inside the ink supply station and cannot be removed.
Typically, a depressurization sequence is opposite of the above described pressurization sequence. In the depressurization sequence, the air pump is temporarily disconnected and the air solenoid valve is closed to reduce the air pressure on the ink supply to approximately about 0.25 PSI. At this point, the ink solenoid valve is closed and the ink supply can be replaced with another ink supply. The opening and closing of solenoid valves, such as the air solenoid valve and ink solenoid valve can be very time consuming. Typically, each of the solenoid valve operations (i.e., opening or closing valve operations) takes about 0.5 sec to complete. Once the air pump is temporarily disconnected, the time taken for the solenoid valve operations may cause the air pressure on the ink supply to drop significantly and the drop in the air pressure can be very difficult to control.
Also, in the case where the ink supply station is mounted at the negative Z elevation below the print head, the air pressure on the ink supply drops exponentially from 6 PSI to 0.25 PSI, which may result in a negative pressure at the septum. The negative pressure at the septum may cause air bubbles to be formed in the ink tube leading to a dry firing of pens in the inkjet printing device or damage in the print head. Further, the air bubbles can cause degradation of print quality.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.